The present invention relates generally to ring seals, and more particularly to adjustably sizable ring seals.
Ring seals or spring gaskets are often used in various systems to provide a seal between opposing or mating surfaces to prevent pressure leakage, and particularly where high temperature and/or corrosive conditions are encountered. For example, it is now commonplace to use ring seals to minimize leakage of either compressed air or combustion products in jet engines between circumferentially-extending, spaced-apart, opposing sections of the engine.
Typically, the flanges in the jet engine where such ring seals are used are made from a multitude of segments bolted and interlocked together. Certain joints are made to fit closely and yet are slightly separated to allow for the differential thermal expansion of the various parts. Cavities between the flanges are provided to contain flexible metal ring seals to assist in forming the differing pressure boundaries.
In jet engines, between startup and elevated temperatures (e.g., about 1200 degrees F.), typically axial deflection of the mating parts is about 0.030 inch. Differential radial movements of the parts may be as much as 0.100 inch.
Of particular concern is the differential expansion of the lighter metal parts, such as the ring seals, during initial operation of the engine at which time the temperature of the ring seal may increase faster than the surrounding flange parts which typically have thicker cross-sections.
It has been conventional practice to make a circular ring seal and remove a small segment from the circumference, thus creating a gap of about xc2xc to xe2x85x9c inch between end portions of the ring seal. Such a ring seal is disclosed in applicant""s earlier issued U.S. Pat. No. 3,751,048, the contents of which is incorporated herein by reference in its entirety.
The gap closes when the ring seal expands; typically when the jet engine containing the ring seal is heated rapidly, and then opens again when the temperature of the jet engine stabilizes. Undesirably, the gap allows fluid, for example lubricants, pressurized air, or combustion gases, to escape through the seal thereby resulting in leakage and loss of engine performance. However, if the gap is not provided or if improperly sized, the ring seal becomes distorted and permanently deformed when it expands during the heating portion of the cycle such that it will no longer fit closely to the flange as designed resulting in further leakage and loss of engine performance.
Other ring seals have included a ring seal element which is sized having spaced-apart end portions and a separate connecting member. The separate connecting member extends across the spaced-apart end portions of the ring seal element. The separate connecting member is typically attached to one end portion of the ring seal element by welding or riveting.
Drawbacks with the above-noted two-piece ring seal include additional manufacturing steps, e.g., separately fabricating the ring seal element and the connecting element, and additional assembly steps, e.g., aligning and attaching the connecting element to one of the end portions of the ring seal element. In addition, by welding or riveting the connecting element to the ring seal element, stresses are introduced in the ring seal which can effect the ability of the ring seal to provide a proper seal.
Therefore, there is a need for a low cost, desirably one-piece, adjustably sizable, ring seal operable to readily circumferentially expand and contract in size in response to varying operating conditions such as varying temperatures, pressures, loads, etc. while minimizing leakage of fluid through the ring seal.
The above-mentioned drawbacks are overcome by the present invention which provides an adjustably sizable ring seal comprising a monolithic ring having a first end portion having a first cross-section and a second end portion having an integrally formed reduced cross-section slidably receivable generally within the first cross-section and/or an integrally formed radially offset cross-section slidably receivable generally within the first cross-section so that the monolithic ring seal is circumferentially expandable and contractable in size.
Desirably, the ring seal is fabricated from one-piece and the first cross-section and the second cross-section comprise generally corrugated cross-sections. Advantageously, the ring seal comprises a body portion between the first end portion and the second end portion, the first end portion and the main body portion defining a gap therebetween across which the second end portion extends, and the gap being substantially closed when the ring seal is disposed in a contracted configuration between the at least two circumferentially-extending spaced-apart members
In another aspect of the present invention, a method for forming an adjustably sizable ring seal includes providing a continuous generally circular-shaped ring having a first cross-section, forming a portion of the ring into at least one of a reduced cross-section and a radially offset cross-section, and cutting the ring so that the ring comprises a first end portion having the first cross-section and a second end portion slidably receivable within the first cross-section so that the ring seal is circumferentially expandable and contractable in size.